The Radiation Core will provide the irradiation in support of all of the projects in the program. This core is housed in the Lombardi Cancer Center and currently consists of a J.L Shepard Mark I, Model 30, Cesium Irradiator. This Mark I is specifically designed for experimental gamma-irradiations. It contains a 2,200 Ci 137 Cs source. Tissue culture flasks are irradiated by stacking them on the rotating platform. A special rotating tube holder can accommodate test tubes with volumes up to 50 ml. A pie-shaped rotating mouse holder allows simultaneous whole-body irradiations of a dozen mice at a time. The cesium irradiator is suitable for the majority of the irradiations required by this program; however, the inability to effectively focus and block the beam makes it difficult to use the instrument for partial body irradiations, such as tumor irradiations in the flanks of mice. Also, the penetrability of the radiation cannot be controlled because the photon energy cannot be modulated. For these reasons, we are requesting the purchase of a low cost, portable, x-ray machine, that cannot be dedicated to the experimental work of the program. The requested x-ray machine is the RS2000, manufactured by Rad-Source, a division of Microfocus Imaging, Inc of Wheeling, IL. Dr. Timothy Jorgenson is Director of the Radiation Core. His responsibilities include training personnel in the proper and safe use of the instruments, and ensuring compliance with NRC regulations. Dr. Jorgenson chairs an Internal Advisory Committee. The Committee meets as needed to set rules and policies from instrument use, and to make decisions concerning maintenance and repairs. The committee guarantees fair and equitable use of the instruments among the investigators.